Darrin just reminds me of
Bobby Darin, the 50s singer. It does look better than
Darren, though.
How about Daron? It's a genuine Welsh name, although not very common; comes from the Daron river (
Afon Daron) in North Wales, the name for which is based on an old Welsh word for oak. I just looked through the Darons born between 1984 and 2005 here, and saw Daron
Vaughan, Daron
Martin, Daron
Charles, Daron
Robert, Daron
Benedict, Daron
William and Daron
Thomas, which all sound quite good to me.